What is the second number in the row of Pascal's triangle that has 43 numbers?
Solution: The row 1, 1 has 2 numbers.  The row 1, 2, 1 has 3 numbers.  The row 1, 3, 3, 1 has 4 numbers.  Each time we go down one row, we have one more number in the list.  So, the row that starts 1, $k$ has $k+1$ numbers (namely, the numbers $\binom{k}{0}, \binom{k}{1}, \binom{k}{2}, \ldots, \binom{k}{k}$.)  So the row with 43 numbers starts 1, $\boxed{42}$.